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Truck still running rich

Discussion in 'Chevy C/K Truck Forum' started by okysmokey911, Sep 23, 2010.

  1. okysmokey911

    okysmokey911 Rockstar 100 Posts

    I am still having a problem with my truck running really rich... lots of black smoke out the tail pipe and the smell of gas is obvious. So far I have done the following, checked all vacuum lines, replaced 02 sensor, engine temp switch, coolant temp sensor, set timing with timing light, replaced tps, and I still cannot find the problem. I am not throwing any codes soo I have no idea what is going wrong. I believe the only two things I have not replaced ( because they are somewhat new) are the idle air control and the MAP sensor. Is there anything else it could be?

    truck is a 93 k1500 with a newly rebuilt 5.7 350. The engine was built with the edelbrock 3702 cam, bored 60 over, flat top forged pistons, high volume oil pump, and all the rest was stock.

    MANBEARPIG New Member

    hmmmm. I would normally keep my mouth shut on vehicle I cant look at but I have seen similar problems from leaking throttle body injector assemblies and too high fuel pressure. Also make sure you disconnected the electronic advance before setting timing
  3. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    X2 on disconnecting the timing advance, but also you could have a problem with the advance in the distributor not working properly. I would pull the IAC out and check for carbon as well.
  4. okysmokey911

    okysmokey911 Rockstar 100 Posts

    So a bad IAC could be causing the problem? I did unplugged the timing advance when I was setting the timing so I dont think that is the problem. Is there any way to check and see if the timing advance on the distributor is not working? I am not sure if this is normal or not, but when I set my timing to 0 after unplugging the electronic advance and then plug the electronic advance again, the timing mark on the harmonic balancer goes so far away that its almost out of sight like the computer is advancing the timing by a large amount. So I dont know if that is normal or not? I know the whole tbi system is not leaking so thats not an issue.......
  5. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    The IAC usually causes a lean condition. But it never hurts to clean it out. And there is a chance that the Pick-up coil is bad or shorted, i had a similar problem but i just had no power.
    Im not to sure on the specifics of the 3702 cam, but that has a considerable bump in lift and duration isnt it? because you may actually require a custom tune to run that, Also the computer may be over compensating for the increase in cyl volumn thinking that it is running lean. that is the issue with the OBDI system is it doesnt have as much of a reading to keep the EFI in check.
    Also when was the last time you did a sweep test on the Throttle position sensor. I doubt its the culprit but im wondering if the computer isnt thinking that the throttle is open alot further than it is and allowing for greater fuel flow..
  6. okysmokey911

    okysmokey911 Rockstar 100 Posts

    well I just took apart the throttle body and checked out some of the sensors and I believe that I do have an Iac problem. I noticed that my Iac was a little loose and that when I tightened it, the truck would even idle so I am thinking its stuck. I replaced the tps like 3 weeks ago so I dont think its the tps. I was also thinking that the pick-up coil could be the culprit. Right after the rebuild the engine did not run so rich so I dont think the cam is causing any issues. You are right about the obd1 though.
  7. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Well start with the small stuff since that is the stuff that i end up needing and overlooked for 2 weeks HAHA
  8. okysmokey911

    okysmokey911 Rockstar 100 Posts

    yeah I have pretty much gone through all of the little stuff. after taking everything off and putting it back on I am now getting a tps error code I just dont understand why because the tps is brand new... i guess it could be faulty. There is one more thing I would like yalls opinion on. I have the holley 502-9 throttle body on there and I noticed that the injectors are a lot louder than they used to be. Is it possible that they are stuck open? this particular holley has the adjustable tps which used to control the idle, but now adjusting it does nothing to the idle. To test the injectors do you use ohms or voltage? Its probably voltage right?
  9. okysmokey911

    okysmokey911 Rockstar 100 Posts

    Soo I am pretty sure I found the culprit... I now believe it was the cap and rotor. At first i didnt think it would be the cap and rotor because I had recently replaced both, but when I took the cap off I noticed that the cap and rotor both had corrosion built up on all the points soo I am guessing not enough electricity was passing through. The exhaust still smells a tid bit rich, but not near as bad as it was before. I was honestly embarrassed to stop at a stoplight before because the exhaust was so rich. I will update to see if that really was the issue. Just goes to show how much time ( and money ) you can save by doing the little things.
  10. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    As to your faulty TPS yes that is more than likely bad since you cant adjust it, and ive had them come out of the box bad more than once. And hopefully your getting all the kinks worked out.

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